Biogenic pentagonal silver nanoparticles for safer and more effective antibacterial therapeutics.

Background: Biological synthesis of nanomaterials possesses unprecedented potential in the production of nanomaterials due to their ability to produce nanomaterials with improved biocompatibility in addition to eco-friendly synthetic procedures.

Methods: This article reports the isolation of an air-borne fungus from the campus of Integral University, Lucknow, with an exceptional ability to withstand very high concentrations of silver salt. The fungus was found to produce pentagonal silver nanoparticles (AgPgNps) when silver ions were reduced from silver nitrate. Molecular analysis and biochemical characterization techniques based on 18-seconds rRNA identified the fungus to belong to the Aspergillus sp. with the NCBI accession no KF913249. Material characterization techniques including ultraviolet (UV)-visible spectroscopy, transmission electron microscopy, and zeta potential analysis were used to satisfactorily characterize the as-synthesized AgPgNps.

Results: The AgPgNps synthesized by the fungus Aspergillus sp. exhibit an absorption that is maximum centered at about 416 nm, with a standard particle size of 23.22±2 nm. These AgPgNps exhibited broad-spectrum antimicrobial activities against an array of bacterial pathogens with remarkable minimum inhibitory concentration (MIC50 ) values: Staphylococcus aureus (ATCC 25923) - 9.230 µg/mL, Bacillus sp. (ATCC 14593) - 12.781 µg/mL, Escherichia coli (ATCC 25922) - 5.063 µg/mL, and Klebsiella pneumoniae (ATCC 13883) - 5.426 µg/mL. In vitro cytotoxicity analysis of biosynthesized AgPgNps showed a dose-response activity against human cervical cancer cell line (HeLa) and adenocarcinoma cells (A549) with MIC50 values of 0.038 µg/mL and 0.044 µg/mL, respectively.

Conclusion: These findings are very crucial to evaluate the biosynthetic process for the synthesis of nanoparticles (NPs) with unique properties. These NPs may find potential applications in sensing, medicine, and antimicrobial and anticancer therapies.